1. Technical Field
The present invention relates to a correction circuit and a test apparatus. In particular, the present invention relates to a correction circuit for generating an output signal emphasizing a predetermined signal component of a given input signal, and to a test apparatus for testing a device under test using the correction circuit.
2. Related Art
A test apparatus for supplying a test signal to a device under test and testing a signal under measurement outputted from the device under test is considered as a type of apparatuses for testing a device under test such as a semiconductor circuit. The acceptability of the device under test can be determined for example by examining whether a normal signal under measurement is outputted.
A transfer path for transferring signals is provided between the test apparatus and a device under test. However, a resistance, a capacity, and the like exist in the transfer path, which degrades the signal waveform. As a means to cope with this problem, a technology is already known to generate a test signal to be inputted to the device under test, by compensating for the loss in the transfer path of the waveform of the test signal (see for example Patent Document No. 1). There is also known a technology to compensate for the loss in the transfer path of the signal received from the device under test.    Patent Document No. 1: Japanese Patent Application Publication No. 2006-337140
One compensation method for loss is to generate a correction signal in accordance with the waveform of the original signal, and add the generated correction signal to the original signal. Such a correction signal can be generated by generating a differentiated waveform of the original signal, and amplifying the differentiated waveform in accordance with the amount of loss in the transfer path.
However, when the amplification factor of the differentiated waveform changes, the direct current component applied to a correction signal occasionally also fluctuates. By generating an output signal by adding a correction signal to an original signal, the direct current component of the output signal fluctuates in proportion to the amplification factor of the differentiated waveform, to degrade the direct current voltage accuracy of the output signal after the correction.
In addition, when compensating for the transfer path loss of a differential signal, the correction signal is required to be generated for each of the non-inversion signal and the inversion signal for the differential signal. In such a process, if variations are caused in the direct current components among correction signals for example due to characteristics variation in the elements generating these correction signals, the direct current voltage accuracy of the differential signal after correction will degrade.